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Asbestos fibers penetrate organs at the microscopic level and protrude though the organs into the body cavity. It can produce number of fatal illnesses.
The fibers have got some carcinogenic effect and can mutate the body cells. A cell has got the capacity to divide by mitosis or miosis. The cell division occurs in a regular manner and is uniform in particular type of cells. When the fibers mutate the body cells it becomes cancerous and multiply in an abnormal manner. These cancerous cells can move towards other sites and can form tumors wherever they reach.
Asbestos related diseases affect mainly the respiratory system. Even small amounts of asbestos can inflict irreversible damage. When the fibers are inhaled or ingested, it becomes a health hazard and life-threatening.
Asbestos fibers can enter in to the respiratory tract of employees working in asbestos mines, shipyards, asbestos factories, Industries where asbestos is used as a raw material, heating and construction industries etc.
The suspended fibers in the air will enter into the respiratory tract and are attached to the mucus surfaces, which will be removed by the mucociliary mechanism. Mucus cells in the tract secrete the mucus and the sticky mucus will engulf the dust particles. By the action of cilia in the tract the particles attached to the mucus is removed out.
By this way a large amount of fibers are removed. Small fibers will be deposited in the wall of respiratory bronchioles and are phagocytosed by the macrophages, which are specialized cells. The macrophages retain the absorbed particles in the alveolar epithelium. An iron containing protein ferritin is secreted and will form a covering on the surface of absorbed asbestos particles. By this way brownish asbestos bodies are formed.
The activated macrophages will secrete cytokines and chemical mediators of inflammation, which in turn damages the lung parenchyma. The action of all chemical mediators damages the lung parenchyma
resulting in alveolitis. The above process results in lung fibrosis. The alveoli get collapsed and the affected area becomes hard and oxygenation in that area is affected. If this process continues it results in respiratory insufficiency and death.
Asbestos can also enter in to pleura and peritoneum leading to fibrosis and all other malignant lesions.
The diseases produced by the asbestos can be broadly classified to benign diseases and malignant diseases.
1) Benign asbestos diseases:
These are also called non-cancerous asbestos diseases. The main pathology here is lung fibrosis due to the entry of fibers. Asbestos diseases are progressive which will not stop though the exposure is stopped. The clinical manifestations of these diseases appear in the terminal stage of the disease. Once the lung is fibrosed it can't be restored to the normal stage. There are mainly two types of benign asbestos diseases.
a) Benign pleural diseases
b) Asbestosis
Benign Pleural diseases
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They are of three types.
i) Pleural plaque:
Here discrete local area of pleural thickening is formed in the parietal pleura on the chest wall and the diaphragm. This affects only a small area and may be unilateral. Pleural plaques will not affect the lung function seriously.
ii) Diffuse pleural thickening or fibrosis:
Here the fibrosis is bilateral and adhesions are formed between visceral and parietal pleura. The thickened pleura impede lung expansion leading to breathlessness. The chest wall movement is also affected.
iii) Asbestos pleurisy with effusion:
Here the pleura gets inflamed with collection of fluid in the pleural cavity. It is called pleural effusion.
Asbestosis
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It is a non-cancerous chronic disease of the lung due to exposure to asbestos fibers. There is pulmonary parenchymal fibrosis, which occurs several years after exposure. The fibrosis is peribronchial, diffuse in character and basal in location.
Initially there is shortness of breath which is aggravated by exertion and if progresses gets dyspnoea even by small exertion. Cough is non productive initially. In the beginning stage fine crackles are heard (with the help of stethoscope) in the lower zones and later it becomes generalized. When the disease advances there will be central cyanosis and signs of pulmonary hypertension and corpulmonale.
Findings in asbestosis: X-ray of the chest shows scattered small, irregulars or linear opacities in the lower and mid lung zones. High resolution computed tomography gives more information than X-ray. There is sub pleural curvilinear opacities, parenchymal bands, increased inter lobular septa, honey combing of the pulmonary parenchyma etc. Pulmonary function test reveals restrictive ventilatory defect and impaired gas transfer.
Sputum contains asbestos bodies along with inflammatory cells. Asbestosis usually progresses slowly and can be fatal it not treated properly.
2) Malignant asbestos diseases:
Carcinogenic properties of asbestos fibers can mutate the cells that come in contact with them. There are two types of cancers seen in asbestos exposed workers.
A) Bronchogenic Carcinoma.
B) Mesothelioma.
Bronchogenic carcinoma:
Asbestos exposure increases the chance for all histologic types of bronchogenic carcinoma. Cigar smoking and asbestos exposure act synergistically to increase the risk. The occurrence of carcinoma is high in those exhibiting pulmonary fibrosis as a result of asbestos exposure.
Mesothelioma:
Mesothelioma is the tumor of the mesothelial cells, which form the lining over the lungs (pleura), heart (pericardium) and abdominal organs (peritoneum).
Mesothelioma is commonly seen on the pleura, which forms the covering of the lung. Two layers of mesothelial cells called parietal and visceral pleura cover the lung. In between the pleura these is a pleural cavity, which is moistened by a fluid called pleural fluid. The main function of pleura is protection. It helps to create a negative pressure in chest cavity, which is essential for the process of respiration. The movement of lungs during respiration is made frictionless by the presence of pleura and pleural fluid. Mesothelioma may also affect the peritoneum, which is a mesothelial tissue in the abdomen. The peritoneum covers the abdominal organs. It is also having two layers. The outer parietal peritoneum is attached to the inner wall of the abdomen. Inner visceral peritoneum is attached to the abdominal organs. In between the two layers there is a cavity called peritoneal cavity. Very rarely mesothelioma affects the pericardium. It is the covering seen around the heart. It is also having two layers, fibrous pericardium and serous pericardium.
Mesothelioma may be benign or malignant but rarely is it benign. Malignant Mesothelroma is relatively rare but for those who are affected it is a disaster.
70% of all the cases of malignant Mesothelioma are pleural. 10 to 20% are abdominal affecting the peritoneum. Pericardial mesothelioma is very rare. Mesothelioma is an extremely malignant and incurable cancer.
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